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Urban flooding, fueled by climate change and rapid urbanization, presents significant challenges for cities around the world. In the United States, this is of particular concern as we see older cities reaching their maximum development density, and newer cities developing to the edge of their boundaries. The dynamic nature of cities and the people that live in them complicate urban flood risk modeling. This paper highlights the need to reconceptualize urban flooding from a spatially and temporally intersectional perspective by analyzing the patterns of socio-economic and bio-physical data across eight US cities to illustrate how spatial flood risk is driven by place-specific factors. Here, we demonstrate the need for a holistic understanding of flood risk, which acknowledges both the deep histories and uncertain futures specific to each city to promote urban flood resilience and environmental justice. Legacies of racialized development continue to influence the spatial heterogeneity of urban flood risk. Thus, centering the ways past injustice has shaped the environment is critical to highlighting inequities in who and where is at increased risk of flooding. The varying impacts of climate change on flooding in different cities, as well as the actions city governments have taken in response to flood events, inform risk and should be included in modeling efforts. There are many challenges in incorporating new temporal dynamics into flood risk modeling, such as data availability, creating a necessity for a greater understanding of flood impact. This is required not only to fully comprehend the impacts of flooding but also to identify appropriate, necessary, and community-sensitive flood interventions as well as to optimize the impact of adaptive measures. Considering historical and future drivers of risk, intersectional flood risk models are required to promote more equitable and effective resilience efforts. This approach will allow urban flood planners and engineers to gain a deeper understanding of how to promote climate resilience while overcoming the reinforcement of discriminatory development and management patterns. 

Abstract Accurately delineating both pluvial and fluvial flood risk is critical to protecting vulnerable populations in urban environments. Although there are currently models and frameworks to estimate stormwater runoff and predict urban flooding, there are often minimal observations to validate results due to the quick retreat of floodwaters from affected areas. In this research, we compare and contrast different methodologies for capturing flood extent in order to highlight the challenges inherent in current methods for urban flooding delineation. This research focuses on two Philadelphia neighborhoods, Manayunk and Eastwick, that face frequent flooding. Overall, Philadelphia, PA is a city with a large proportion of vulnerable populations and is plagued by flooding, with expectations that flood risk will increase as climate change progresses. An array of data, including remotely sensed satellite imagery after major flooding events, Federal Emergency Management Agency’s Special Flood Hazard Areas, First Street Foundation’s Flood Factor, road closures, National Flood Insurance Program claims, and community surveys, were compared for the study areas. Here we show how stakeholder surveys can illuminate the weight of firsthand and communal knowledge on local understandings of stormwater and flood risk. These surveys highlighted different impacts of flooding, depending on the most persistent flood type, pluvial or fluvial, in each area, not present in large datasets. Given the complexity of flooding, there is no single method to fully encompass the impacts on both human well-being and the environment. Through the co-creation of flood risk knowledge, community members are empowered and play a critical role in fostering resilience in their neighborhoods. Community stormwater knowledge is a powerful tool that can be used as a complement to hydrologic flood delineation techniques to overcome common limitations in urban landscapes.